Yes, the difference in electricity potential between one side of the membrane and the answer can be measured. This is of great importance to neurons and muscle cells. For example, the neuron has a potention of 70mV, negative in the interior. Is this what you mean?

"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter